Recycling C&D Waste

70 per cent of the construction industry is not aware of recycling techniques. Read on for effective solutions!

The numbers say it all. At present, India is among the top 10 countries in the world generating the highest amount of municipal solid waste. And the bigger challenge is that about 70-75 per cent of this waste remains untreated.

For instance, Anup Mathew, Senior Vice President & Business Head, Godrej Construction, shares, 'In Jaipur, 1,300 tonne per day (tpd) of municipal solid waste is produced, of which 274 tpd construction waste material is lifted from roadsides near building sites. It is estimated that 941 tpd construction waste is produced in the entire state of Rajasthan.' Further, according to an estimate prepared by the Building Materials and Technology Promotion Council (BMTPC) and Centre For Fly Ash Research and Management (C-FARM) in 2016, the construction waste generated annually is around 165-175 million tonne. While Delhi generates about 5,000 tonne daily, Mumbai generates about 3,000 tonne, followed by Kolkata at 2,000 tonne and Chennai at 1,500 tonne. Sharing such facts and more, Mathew offers effective solutions to treat the generated waste.

In 2012, the government had directed states to set up construction waste facilities in all cities with a population of over 10 lakh. While there are not many such facilities operational yet, efforts have been made to set up more facilities and reduce the amount of waste dumped at landfills.

Converting waste-to-energy or reusable materials
Waste-to-energy technologies convert waste matter into various forms of fuels that can be used to supply energy. Waste feed stocks can include municipal solid waste (MSW), waste plastic and paper, agriculture and organic waste, industrial waste from agri-based products, coal mining and even the gases that are naturally produced within landfills.

When structures made of concrete are demolished or renovated, concrete recycling as per codal provisions of design is a method to utilise the rubble. We are one of the few organised players who have invested in this machinery. Concrete was once routinely trucked to landfills for disposal but recycling has several benefits that have made it a more attractive option in this age of greater environmental awareness, more environmental laws, and the desire to keep construction costs down.

Concrete aggregate collected from demolition sites is put through a crushing machine. Crushing facilities accept only uncontaminated concrete, which must be free of trash, wood, paper and other such materials. Metals such as rebar are accepted as they can be removed with magnets and other sorting devices and melted down for recycling elsewhere. The remaining aggregate chunks are sorted by size. Larger chunks may go through the crusher again. After crushing has taken place, other particulates are filtered out through a variety of methods.

C&D wastes are largely inert.
The process of segregation of the various components of mixed waste often requires advance technologies, making it difficult to adopt the process across cities. However, simple processes like crushing and recasting for creating non-structural and non-load bearing components like paver blocks, curb stones, fencing poles, etc, can be deployed locally through the route of social entrepreneurship at the point of generation for recycling C&D waste.

Potential of recycling

C&D waste
Bricks, tiles, timber and metals are usually part of the waste generated from C&D sites. For instance, bricks from demolition sites can be recycled as road base and construction fill as well as lightweight concrete. Construction debris consisting of bricks can be recycled into brick aggregate through screening, crushing, re-screening and blending, which can then be used as pavement base material by proper mix proportions with cement and fly-ash. Brick waste that is not suitable for recycling into pavement base materials can be used in construction or landfill.

Generally, it is difficult to extract tiles from the walls in proper shape and size to find them suitable for reuse. Still tiles extracted from walls, even if these are broken pieces, provide an excellent opportunity to artists or designers to make murals or other decorative pieces. Broken tiles can also be used as aggregate after crushing. If tiles can be extracted or removed from the wall in good shape and size, these are reused for the same purpose after the removal of stuck-up mortar and then glued with suitable adhesives available in the market today. Creative items like artefacts, table tops, special effects in driveways, pedestrian subways, etc, can be smartly created by reusing for a wide variety of projects.

A first-of-a-kind processing facility to treat this kind of waste will come up in Indore on 4 acre in the Devguradia region. The treated waste will then be reused to make bricks, pavers block, chairs, and other green products. Indore Municipal Corporation will provide about 75 tonne of waste to the processing facility every day, after collecting the debris from different sites falling within the corporation's limits. There will be no waste discharge from the plant and all the final products will be certified as green and eco-friendly by the Indian Green Building Council (IGBC).

Also, Godrej Construction has recently started recycling concrete waste by making blocks, thus taking a big leap towards providing a reliable avenue for diverting construction waste from going to the landfill. This manufacturing facility in Mumbai can help address this problem within the municipal corporation limits, providing resource conservation while addressing the C&D waste problem. To ensure that the life-cycle approach for responsible products manufacturing is transcended across the value chain, the company involves customers and suppliers, and helps them understand guidelines for managing natural resources, legal obligations and operational requirements by providing a checklist at the time of handover.

Managing waste
Delhi, Mumbai and Kolkata top the list of cities that generate a huge quantity of demolition waste (debris). Hyderabad, Pune, Lucknow, Gurgaon and Jaipur generate debris in the range of 500 tonne to 1,000 tonne. To make builders and contractors responsible, the government has asked states and municipalities to promote recycling of waste for reuse in construction in the context of shortage of natural building materials like sand and to address environmental issues. This can also be achieved for incorporating green building norms in local development control rules, especially for large-scale construction and redevelopment projects, thereby achieving maximum waste diversion from landfills at the source of generation itself.

Going by the law
The Municipal Solid Wastes (Management and Handling) Rules, 2000, published vide notification by the Government of India in the erstwhile Ministry of Environment and Forests, provided a regulatory framework for management of MSW generated in urban areas. To improve the collection, segregation, recycling, treatment and disposal of solid waste in an environmentally-sound manner, the Ministry of Environment, Forests and Climate Change redrafted these rules as Solid Waste Management Rules, 2016, with a separate set of rules for C&D waste called Construction and Demolition Waste Management Rules, 2016.

The rules shall apply to all who generate construction and demolition waste such as building materials, debris, and rubble waste resulting from construction, remodelling, repair and demolition of any civil structure of an individual, organisation or authority. The rules also explicitly mention the role of various stakeholders such as waste generators, service providers, local authority, operators of C&D waste recycling facility, state government, state pollution control boards, Central Pollution Control Board, Bureau of India Standards, and the Central Government, with a mention on the definite timeframe for implementation of these rules at various levels.

Key suggestions
The major components of C&D waste are cement concrete, bricks, cement plaster, steel (from RCC, door or window frames, roofing support, railings of staircase, etc), rubble, stone (marble, granite, sandstone) and wood (especially from demolition of old buildings), while minor components include conduits (iron, plastic), pipes (GI, iron, plastic), electrical fixtures (copper or aluminium wiring, wooden baton, plastic switches, wire insulation), panels (wooden, laminated) and others such as glazed tiles, glass panes, etc. These wastes are best stored at source, ie at the point of generation. Materials that can be reused at the same site for the purpose of construction, levelling, making road and pavement, etc, should be kept in separate heaps from those to be sold or landfilled. Recycling and reuse of these materials basically depends on their separation and condition of the separated material. A majority of these materials are durable and, therefore, have high reuse potential.

However, it would be desirable to have quality standards for recycled materials. C&D waste can be used in the following manner:

Sale or auction of material that cannot be used at the site owing to design.

Rubble, brick bats, broken plaster or concrete pieces, etc, can be used for building activity such as levelling and under coat of lanes where the traffic does not constitute heavy moving loads.

Larger unusable pieces can be sent for filling up low-lying areas.

Fine materials such as sand, dust, etc, can be used as cover material over sanitary landfill.

Construction waste like structural steel can be recycled and used for secondary usages permissible within the limits of design codes.

According to a study commissioned by Technology Information Forecasting and Assessment Council (TIFAC), 70 per cent of the construction industry is not aware of recycling techniques. The study recommends establishment of quality standards for recycled aggregate materials and recycled aggregate concrete. This would help to set up a target product quality for producers and assure users of a minimum quality requirement, thus encouraging them to use it.

- SHRIYAL SETHUMADHAVAN

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